This patent application is copending with application Ser. No. 920,977 entitled "Tandem Wing Universal Vortex Shedding Flowmeter" filed on Oct. 18, 1986.
Experimental studies on the fluid flow around a bluff body have proven the fact that the bluff body sheds a series of vortices from the two opposite cylindrical sides thereof in an alternating pattern at frequencies proportional to the fluid velocity at Reynolds number as low as a few hundred and as high as a few million. It has been proven that the vortex shedding frequency is directly proportional to the fluid velocity in a range of Reynolds number greater than 1,000 and less than 100,000. Consequently, a perfect vortex shedding flowmeter should operate in the aforementioned range with hundred to one turn-down ratio. For example, a perfect vortex shedding flowmeter should measure the air flow velocity as low as 5 feet per second and as high as 500 feet per second under the standard condition and water flow velocity as low as 0.4 feet per second to 40 feet per second. With few exceptions, the existing vortex shedding flowmeters available in the present day commercial market operate in a much reduced range with twenty to one turn-down ratio, wherein these existing vortex shedding flowmeters are unable to measure air velocities less than 15-20 feet per second and water velocities less than 1-2 feet per second.